1. Field of the Invention
This invention relates to hydroxy fatty acids, a process for their production, and estolide intermediates. The hydroxy fatty acids and estolides are useful as lubricants, greases, plasticizers and printing inks, as well as in cosmetics.
2. Description of the Prior Art
Unsaturated fatty acids have been used in the past for the production of dimer acids by a variety of techniques, including clay catalyzed reactions, as reviewed by Johnson ["Dimerization and Polymerization," in: Fatty Acids, E. H. Pryde (ed.), AOCS, (1979), pages 343-352] and Leonard [in: Encyclopedia of Chemical Technology, Kirk-Othmer, John Wiley & Sons, third edition, volume 7, (1979)]. Depending upon the fatty acid feed, the dimer acids were produced together with monomer acids, and ranged in structure from acyclic to monocyclic to polycyclic. In accordance with the goals of these prior art processes, reaction conditions were selected to maximize yields of these dimer acids. No estolides have been reported or identified as products of any of these previous methods.
Yamaguchi et al. [Japanese Patent No. 213,387, (1990)] recently described a process for enzymatic production of estolides from hydroxy fatty acids present in castor oil using lipase. However, such estolides would be composed of esters at the 12 carbon of the fatty acids.
Hydroxy fatty acids have also been described, and are useful as lubricants and greases and in cosmetics. However, there is no domestic commercial source of hydroxy fatty acids currently available. The hydroxy fatty acids are derived from castor oil which must be imported.